Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that is characterized by the loss of motor neurons, leading to progressive decline in motor function and ultimately death. The motor symptoms of ALS include muscle weakness, twitching and wasting, which leads to difficulties in speaking, swallowing and breathing. The cause of motor neuron death in ALS is unknown and 5-10% of the ALS cases are inherited.
Activation of immune cells in the central as well as peripheral nervous system has been suggested to be a critical determinant of disease progression in ALS (Phani et al, Front Pharmacol. 3:150, 2012). Specifically, microglia and macrophages have been shown to play distinct roles in the orchestration of neuroinflammation in this disease (Dibaj et al, PLoS One. 6(3):e17910, 2011; Boillee et al, Science, 312:1389-92, 2006). Of note, bone marrow transplantation (BMT) to replace host myeloid cells has been shown to extend survival in an animal model of ALS, which was thought to be mediated by replacement of CNS microglia (Beers et al, Proc Natl Acad Sci USA. 103:16021-6, 2006). However, recent studies have shown that these cells do not develop from bone marrow cells but from more primitive yolk sac progenitors (Ginhoux et al, Science, 330:841-5, 2110), suggesting that the bone marrow derived cells that mediated the therapeutic effects of BMT in the study above are more likely peripheral or brain perivascular macrophages. Nevertheless, specific signaling pathways that contribute to innate-immune-cell-mediated inflammation in ALS remain incompletely understood.
Currently, there is no cure for ALS. Certain therapies such as riluzole, bone marrow transplantation (Deda, Cytotherapy. 11:18-25, 2009), and non-invasive ventilation (McDermott et al, BMJ, 336:658-62, 2008) have shown modest effects in improving quality of life and extending survival, but none are curative or provide dramatic benefit.
Alzheimer's Disease
Alzheimer's Disease (AD) is a degenerative brain disorder characterized clinically by progressive loss of motor function, in addition to memory, cognition, reasoning, judgment and emotional stability that gradually leads to profound mental deterioration and ultimately death. Neuronal metabolic dysfunction in the form of oxidative stress has been proposed to be an underlying cause of neurodegeneration in AD (Friedland-Leuner et al Mol Biol Transl Sci, 127:183-201, 2014).
Although AD develops differently for every individual, there are many common symptoms. Early symptoms are often mistakenly thought to be age-related concerns, or manifestations of stress. In the early stages, the most common symptoms are motor decline and difficulty in remembering recent events, known as short-term memory loss (Buchman et al, Exp Rev Neurother, 11:665-76, 2011). When AD is suspected, the diagnosis is usually based on tests that evaluate behavior and thinking abilities, often followed by a brain scan if available. However, examination of brain tissue is required for a definitive diagnosis. As the disease advances, symptoms can include confusion, irritability, aggression, mood swings, trouble with language, and long-term memory loss. As the person's condition declines, he/she often withdraws from family and society. Gradually, bodily functions are lost, ultimately leading to death.
Parkinson's Disease
Parkinson's disease (PD), also known as idiopathic or primary parkinsonism, is a degenerative neurological disorder of the central nervous system. The motor symptoms of PD result from the death of dopamine-generating cells in the substantia nigra, a region of the midbrain; the cause of this cell death is unknown. Early in the course of the disease, the most obvious symptoms are movement-related; these include shaking, rigidity, slowness of movement and difficulty with fine motor skills, walking, and gait. Later, thinking and behavioral problems may arise, with dementia commonly occurring in the advanced stages of the disease, whereas depression is the most common psychiatric symptom. Other symptoms include sensory, sleep and emotional problems.
PD is characterized by progressive motor impairment and neuroinflammation induced by microglia, the resident immune cells of the central nervous system (Aguzzi et al, Science, 339:156-61, 2013). Inflammatory mediators produced by dysfunctional microglia have been shown to induce neuronal cell death, which underlies the progressive impairment in cognitive and behavioral performance in neurodegenerative diseases (Czirr et al J Clin Invest, 122:1156-63, 2012). Nevertheless, specific signaling pathways that contribute to microglia-mediated inflammation remain elusive.
Huntington's Disease
Huntington's disease (HD) is an autosomal dominant degenerative disorder of the central nervous system, in which the gene Huntington is mutated. HD is an inherited disease that causes the progressive breakdown (degeneration) of nerve cells in the brain. HD has a broad impact on a person's functional abilities and usually results in movement, thinking (cognitive) and psychiatric disorders.
The symptoms of HD vary among affected subjects; however, the progression of the disease is relatively predictable (Mason S et al, J Neurol. 2015). Early in the course of the disease, the symptoms are subtle such as changes in mood. Later, cognition and motor problems may arise, with dementia commonly occurring in the advanced stages of the disease. Chorea (involuntary movement) is the most common motor symptom. Other complications include pneumonia, heart disease, and physical injuries due to falls.
There is currently no cure for HD and full time care is required for subjects with advanced disease.
Frontotemporal Degeneration
Frontotemporal degeneration (FTD) is a disease that is closely related to AD in which progressive degeneration occurs in the frontal and temporal lobes of the brain. Gliosis and inflammatory activation of microglia have been documented in humans and animal models of FTD (Cagnin et al Annals of Neurol. 2004 6: 894-897; Yi et al. J. Exp. Med. 2010. 1:117-128). Patients with FTD experience a gradual decline in behavior and language with memory usually relatively preserved. As the disease progresses, it becomes increasingly difficult for afflicted subjects to organize activities, behave appropriately, and care for oneself. There are currently no treatments to slow or stop the progression of the disease.
Dementia with Lewy Bodies
Dementia with Lewy bodies (DLB) is a type of dementia that is related to PD. The hallmark of this disease is the presence of alpha synuclein aggregates in brains of afflicted subjects. These patients experience PD-like symptoms including hunched posture, rigid muscles, a shuffling walk and trouble initiating movement as well as changes in reasoning and thinking, memory loss (but less significantly than AD). Since Lewy bodies are also present in PD, these two diseases may be linked to the same underlying abnormalities in how the brain processes the protein alpha-synuclein. Furthermore, similar to microglia-related neuroinflammation is present in brains of subjects with DLB, although this pathological feature occurs more extensively (Iannaccone et al, Parkinsonism Relat. Disord. 2013 19: 47-52).
Motor Neuron Diseases
Motor neuron diseases (MND), are neurological disorders, similar to ALS, that selectively affect motor neurons, the cells that control voluntary muscle activity including speaking, walking, swallowing, and locomotor activities. There is no effective treatment for MND. They are neurodegenerative in nature, and cause progressive disability and death. Furthermore, a specific pathway called progranulin can trigger inflammatory activation of microglia in an animal model of MND and genetic ablation of this pathway can delay disease progression (Philips et al. J. Neuropathol Exp Neurol. 2010 69:1191-200).
Demyelinating Diseases
Demyelinating diseases such as Guillain-Barré syndrome and multiple sclerosis (MS) are degenerative disorders in which in which the myelin sheath of neurons is compromised. This damage impairs signal conductivity in the affected nerves, causing deficiency in sensation, movement, cognition, or other functions. There is no cure for these diseases. Its most well-known form is MS, a disease in which the cellular subsets of the immune system have been implicated. For instance, on-going demyelination is often associated with infiltration of T cells and macrophages from the circulation as well as inflammatory activation of microglia (Kutzelnigg et al. Handb. Clin. Neurol. 2014, 122:15-58).
There is a need for an improved method for treating neurodegenerative diseases. The method should be effective and well tolerated.